7-3: cell boundaries - houston independent school district · 2 cell wall • strong supporting...
TRANSCRIPT
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CELL WALL
• Strong supporting layer around the
membrane
• May be present in plants, protists, fungi,
and many prokaryotes
• Main function: to provide support and
protection for the cell
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CELL MEMBRANE
• Regulates what enters and leaves the cell;
provides protection and support
• Made up of two phospholipid layers called
a lipid bilayer
• Referred to as a “fluid mosaic model”
• http://www.dnatube.com/video/360/Fluid-
Mosaic-Model
Cell Membrane Proteins
• Recognition Proteins: cell-to-cell
recognition
• Receptor Proteins: recognize and respond
to different extracellular molecules,
generating specific responses within cell
• Transport (Channel & Carrier) Proteins:
allow specific molecules and ions to pass
through the membrane
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DIFFUSION THROUGH CELL
BOUNDARIES
• Process by which molecules move from areas of
higher concentration to areas of lower
concentration (examples: oxygen, carbon
dioxide, water)
• Continues until equilibrium is reached; particles
will still continue to move
• No energy is required by the cell
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OSMOSIS
• Diffusion of water through a selectively
permeable membrane
• Some water molecules can pass through
cell membrane but most need channel
proteins
• Selectively permeable membrane - some
substances can pass and some cannot
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Effects of Osmosis on the cell
1.Isotonic: concentration is the same on
both sides of the cell. (Normal Cell)
2.Hypertonic: The solution, in which the cell
is in, has higher solute concentration than
the cell. (Skinny Cell)
3.Hypotonic: The solution, in which the cell
is in, has lower solute concentration than
the cell. (Swollen Cell)
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Image source: mywellnesswarehouse.com
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FACILITATED DIFFUSION
• Process that helps large molecules that can’t
pass through the membrane by osmosis
(example: glucose, amino acids)
• Protein molecules act as channels for large
molecules to pass from one side of the
membrane to the other side
• No energy is required by the cell
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ACTIVE TRANSPORT
• Process which does require energy to
transport materials across the cell
membrane
• Movement of molecules against the
concentration differences
• Types of active transport consist of:
– Endocytosis
– Exocytosis
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• Occurs by infoldings, or pockets, of the
cell membrane
• Phagocytosis= “cell eating” cytoplasm
surrounds a particle and package it within
a food vacuole
• Pinocytosis= “cell drinking” tiny pockets
form along the cell membrane, fill with
liquid and then pinch off to form vacuoles
within the cell
Endocytosis